Method for power control for mixed voice and data transmission

ABSTRACT

Power control of mixed voice and data transmissions is disclosed. A voice signal is transmitted at a dynamically-adjusted voice transmit power capped at a maximum voice transmit power limit. Concurrently, data bursts are transmitted on top of the voice signal. Data noise is inserted between the data bursts transmissions. The data burst and inserted data noise are transmitted at a dynamically-adjusted data transmit power based on the voice transmit power to restrict the rate of change of the data transmit power until a maximum data transmit power limit is reached.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present application for patent is Continuation of patent applicationSer. No. 11/241,288 entitled “Method for Power Control for Mixed Voiceand Data Transmission” filed Sep. 30, 2005, currently pending, whichclaims priority to U.S. Pat. No. 7,130,288, filed Jan. 24, 2001, both ofwhich are assigned to the assignee hereof and hereby expresslyincorporated by reference herein.

BACKGROUND

1. Field

The present invention generally relates to the field of wirelesscommunication systems. More specifically, the invention relates todownlink, i.e. from the base station to a set of terminal units, mixedvoice and data transmission for code division multiple accesscommunication systems.

2. Background

In a code division multiple access (“CDMA”) communication system, suchas IS-95, or CDMA2000, or WCDMA (wideband CDMA), transmission can beprovided for voice communication and data communication simultaneouslyby transmitting voice and data signals across one or more communicationchannels. Certain types of signal transmission, for example, voice andcertain types of low data rate data transmissions are degraded by delaysin transmission. Certain types of data signal transmission, on the otherhand, are tolerant of delays in transmission. For example, because thedata is tolerant of delay, the data can be grouped into packets andscheduled for transmission. Furthermore, a delayed packet need not bedropped, and transmission errors can be corrected by simplyretransmitting a packet at a later time, i.e. rescheduling the packet.Large amounts of packet data information can be transmitted efficientlyin short “bursts” of data at high power and high data rate. Conventionalvoice/data transmission treats voice and data communications similarlyby setting up a communication link at a pre-determined data rate, andattempting to transmit voice and data information without exceeding acertain frame error rate. With conventional low data rate voice/datatransmission, changes in the data rate generally do not involvesignificant changes in the overall transmit power; this is because lowdata rate connections only use a fraction of the total power availableat the base station. By way of contrast, transmission of high speedpacket data may require frequent extreme changes in data rate whichtypically involve large changes in power level. Since high data ratetransmission uses a significant fraction of the total base stationtransmit power, the overall base station transmit power level could besignificantly affected by the variation in the power used for high datarate transmissions.

In the present application, voice signal transmission and other signaltransmission which is degraded by delays in transmission, as well asconventional data transmission where changes in the data rate areinfrequent and relatively minor and changes in transmission power levelsare small relative to the total base station transmit power, arereferred to as “voice”. Data signal transmission, such as high speedpacket data, which can be tolerant of delays in transmission and can bescheduled, and typically is transmitted in short “bursts” at high powerand high data rate, as well as any signal transmission where changes inthe data rate are frequent and extreme and changes in transmission powerlevels are relatively large, are referred to as “data”.

In order to efficiently accommodate these different types of signaltransmission simultaneously, i.e., mixed voice and data transmission,different approaches may be followed. One approach is to specify adifferent part of the frequency spectrum, i.e. a different “band” offrequencies or frequency band, for each type of signal. Another approachis to multiplex the voice and data signals together through timedivision. With the time division approach, some of the time availablefor transmitting the signals is allotted to voice signals and some ofthe time available for transmitting the signals is allotted to datasignals. For example, in a GSM+GPRS system (Global System for Mobilecombined with Generalized Packet Radio System) some time slots normallyused for regular GSM voice transmission are instead used for packet datatransmission. One approach, used as an example in the presentapplication, is code division multiple access (CDMA), which allowsmultiple signals to be transmitted at the same time on the samefrequency band.

In CDMA systems each user's signal is separated from other users'signals by modulating the transmission signal with a distinct spreadingcode sequence. The modulation of the transmission signal spreads itsspectrum so that the bandwidth of the encoded transmission signal ismuch greater than the original bandwidth of the user's information. Forthis reason CDMA is also referred to as “spread spectrum” modulation orcoding. Each user uniquely encodes its information into a transmissionsignal using the spreading code sequence. The intended receiver, knowingthe spreading code sequence of the user, can decode the transmissionsignal to recover the information.

By way of background, in CDMA communications, the user's signal isspread to allow many users to simultaneously use the same bandwidthwithout significantly interfering with one another. One means ofspreading is the application of distinct “orthogonal” spreading codes orfunctions, such as Walsh functions, to each user's signal.“Orthogonality” refers to lack of correlation between the spreadingfunctions. In a given spread spectrum communication system using Walshfunctions (also called Walsh code sequences), a pre-defined Walshfunction matrix having n rows of n chips each is established in advanceto define the different Walsh functions to be used to distinguishdifferent user's signals. As an example, for a given sector (or cell inthe WCDMA terminology), each downlink channel is assigned a distinctWalsh function. In other words, communications between a base stationand each user are coded by a distinct Walsh code sequence in order toseparate each user from the others.

The base station transmits signals to all users in a sector so that theWalsh codes are time synchronized in order to achieve orthogonalitybetween the different signals. Effectiveness of the orthogonal spreadingcodes is affected by the phenomenon of “multipath”. Simply stated,multipath is interference caused by reception of the same signal overmultiple paths, that is, multiple copies of the signal arrive afterdifferent path delays. Due to the loss of time synchronization, theorthogonality between different user signals is lost. Interference dueto loss of orthogonality through multipath can be averaged by the use ofother types of spreading codes such as pseudo-noise (“PN”) sequences,for example. The autocorrelation properties of PN sequences can be usedto improve rejection of multipath interference. However, due to the lossof orthogonality through multipath, there is greater interferencebetween the signals of different users, referred to as “intra-cellinterference”, including interference of a user's own signal withitself, also referred to as “self-interference”.

In a multi cell system, there can be interference caused by user signalstransmitted by the base station in one cell interfering with the usersignals transmitted in another cell, also referred to as “inter-cellinterference”. The transmit power of the base station transmitters iscontrolled so as to minimize the amount of power transmitted intoneighboring cells in order to limit inter-cell interference. Extremefluctuations in transmit power can exacerbate the effects of inter-cellinterference, as well as intra-cell interference between users includingself-interference, described above.

FIG. 1 illustrates an example of the effect of data transmission onpower control for multiple voice and data users within the same cell ina CDMA or spread spectrum communication system. FIG. 1 shows graph 100,having power axis 101 plotted against time axis 102. The transmit powerfor a typical voice user varies in time according to single user voicepower curve 104. The aggregate transmission power for all the voiceusers within the cell is shown as Pv 106 in graph 100. Aggregate voicepower Pv 106 varies in time as shown in graph 100. Power is allocated inaddition to aggregate voice power Pv 106 for data burst transmissions108, 109, and 110. The maximum available signal transmission power thatcan be allocated for the total of aggregate voice and data signaltransmissions is maximum power limit Pmax 112, shown in graph 100 as ahorizontal solid line and also indicated by “Pmax.” The data and voiceaggregate transmission power is shown as Pv+d 114 in graph 100. Data andvoice aggregate power Pv+d 114 within the cell varies in time as shownin graph 100. As seen in graph 100, Pv+d 114 remains below maximum powerlimit Pmax 112.

FIG. 1 shows an example of the effect that data signal transmission canhave on power control for a single user in terms of changes to singleuser voice power curve 104. As a result of data burst transmission 108,interference can be increased, due to the intra-cell effects outlinedabove, for the single user whose power allocation is represented bysingle user voice power curve 104. To balance the increasedinterference, power allocation can be increased for the single userleading to local power peak 105 in single user voice power curve 104. Ina conventional voice/data transmission system, changes in powerallocation between users tend to balance out, by occurring randomly intime, leaving only a minor effect on aggregate voice power Pv 106.However, the effect of data burst transmission 108 is simultaneous formany users in the cell, so there is a relatively large effect onaggregate voice power Pv 106, shown as increase 116 in aggregate voicepower Pv 106.

Continuing with FIG. 1, at the end of data burst transmission 108,interference is reduced for the users within the cell. Thus, the powercontrol system at the base station will decrease the power allocation tothe users, leading to decrease 117 in aggregate voice power Pv 106. In amixed voice and data communication system, the power control system mustbe able to respond quickly to changes in interference. Thus, decrease117 in aggregate voice power Pv 106 may be more than needed in view ofsubsequent data burst transmission 109. In other words, the reaction ofthe base station's power control system leading to decrease 117“undershoots” the equilibrium value for stable system performance. As aresult, then, of data burst transmission 109, which again causes anincrease in interference for the users, the base station's power controlsystem increases the power allocation for the users, leading to increase118 in aggregate voice power Pv 106. Once again, increase 118 inaggregate voice power Pv 106 may be more than needed. In other words,the reaction of the power control system leading to increase 118“overshoots” the equilibrium value for stable system performance.

Thus, as shown in FIG. 1, when data signal transmission is mixed withvoice signal transmission in a wireless communication system, thedifferent signal characteristics of voice and data transmissions lead toproblems with power control for users within the same cell. The signalcharacteristics of data communications, namely that data transmissiontypically occurs in bursts, tends to cause disruptions in power controlwhich do not occur with the relatively continuous signal characteristicsof voice communications. For example, over-allocation andunder-allocation of power to each user and to the aggregate of all userswithin a cell can disrupt communications and severely degrade thequality of the communication links. In addition, the system becomessubject to large swings in the total power output, as shown by the largevariations in the level of data and voice aggregate power Pv+d 114,which indicates the total power output of the system.

FIG. 2A, FIG. 2B, and FIG. 2C illustrate an example of some of theeffects of data transmission on power control for users in neighboringcells in a CDMA or spread spectrum communication system. FIG. 2A shows adiagram of cells for exemplary cellular spread spectrum communicationsystem 200 comprising several cells including cell 203, labeled “cell#0” and cell 206, labeled “cell #1.” Despite the use of power controlwithin each cell, out-of-cell terminal units cause interference which isnot under the control of the receiving base station within the cell.Thus, for example, power control within cell 203 can be affected byinterference from the transmission to terminal units in cell 206 andvice versa.

For example, in a mixed voice and data communication system,transmission of data within cell 203 can cause interference in aneighboring cell such as cell 206. The interference in cell 206 causesincreased power allocation to terminal units in cell 206, which is inturn seen as increased interference in cell 203. The increasedinterference in cell 203 can cause increased power allocation in cell203, which originally transmitted the data burst. Thus, there is acomplete cycle of interaction between the power allocation in cell 203and cell 206, which resembles a positive feedback loop. The cycle ofinteraction between the power allocation in cell 203 and cell 206 canlead to higher power consumption than necessary in both cells. Theincreased power consumption in cell 203 and cell 206 can be seen asincreased interference by other neighboring cells, so that the positivefeedback effect spreads power control problems from cell 203 and cell206 to other cells in the system.

An example of feedback effect between two cells only, cell 203 and cell206, is shown in detail in FIG. 2B and FIG. 2C. FIG. 2B shows graph 230,having power axis 231 plotted against time axis 232. The total transmitpower for voice users within cell 203 is shown as aggregate voice powerPv 236 in graph 230. Aggregate voice power Pv 236 varies in time asshown in graph 230. Power for data burst transmission 237 is allocatedin addition to aggregate voice power Pv 236. Maximum power limit Pmax234 that is allocated for the total of aggregate voice and datatransmissions in cell 203 is indicated in graph 230 by horizontal solidline Pmax 234.

FIG. 2C shows graph 260, having power axis 261 plotted against time axis262. Time axis 262 of graph 260 is aligned vertically with time axis 232of graph 230 so that points on time axis 262 in graph 260 alignvertically below the simultaneous points on time axis 232 in graph 230.The total transmit power for voice users within cell 206 is shown asaggregate voice power Pv 266 in graph 260. Aggregate voice power Pv 266varies in time as shown in graph 260. Maximum power limit Pmax 264 thatis allocated for the total of aggregate voice and data transmissions incell 206 is indicated in graph 260 by horizontal solid line Pmax 264.

Continuing with FIG. 2B and FIG. 2C, graph 230 of FIG. 2B shows that thetotal transmit power within cell 203 is represented by aggregate voicepower curve Pv 236, up until transmission of data burst 237. During databurst 237, the total transmit power within cell 203 is substantiallyequal to Pmax 234. After data burst 237, the total transmit power withincell 203 is again represented by aggregate voice power curve Pv 236.Similarly, graph 260 of FIG. 2C shows that the total transmit powerwithin cell 206 is represented by aggregate voice power curve Pv 266. Asdiscussed above, the power increase in cell 203, from Pv 236 toapproximately Pmax 234, during data burst 237 is seen as increasedinterference by the users within cell 206. The increased interference incell 206 leads to higher power allocation by the power control system incell 206. The higher power allocation is reflected in increase 267 inaggregate voice power curve Pv 266. Conversely, increase 267 inaggregate voice power in cell 206 is seen as increased interference bythe users within cell 203 and leads to higher power allocation by thepower control system in cell 203. The higher power allocation by thepower control system in cell 203 is reflected in increase 238 inaggregate voice power curve Pv 236.

The feedback process continues back and forth between cell 203 and 206and can lead to a cell allocating the maximum transmit power available,as shown, for example, by maximum 268 in aggregate voice power curve Pv266. When all available transmit power has been allocated, such as atmaximum 268 shown in graph 230 of FIG. 2C, additional users can bedenied access to the communication system. To the extent that additionalusers would have been able to access the communication system, systemperformance has been degraded. Further the communication link qualityfor the current users may also be degraded. As pointed out above, theeffect can spread from cell to cell and is not restricted to the firstpair of cells. Thus, FIG. 2A, FIG. 2B, and FIG. 2C illustrate an exampleof some of the effects between cells of data transmission on powercontrol in a CDMA or spread spectrum communication system.

As noted above, mixed transmission of voice and data in a CDMA or spreadspectrum communication system can subject the system to large swings orvariations in the amount of transmission power consumed. For example,such large variation is shown in FIG. 1 by aggregate power curve Pv+d114. As shown in FIG. 1, Pv+d 114 varies from approximately one half oflimit of maximum power Pmax 112 to substantially all of Pmax 112. Suchlarge variation, comprising 50% of the maximum power, would be typicalfor mixed voice and data communication systems where half of theavailable power is allocated for voice transmission and half of theavailable power is allocated for data transmission. As seen in FIG. 1and in FIG. 2A, FIG. 2B, and FIG. 2C, the large variation can lead toover-allocation and under-allocation of power to each user and to theaggregate of all users within one cell or several cells in thecommunication system. The resulting instability of power control in thecommunication system can cause serious degradation of system performanceincluding access problems and degradation of communication link qualityfor the users.

Thus, there is a need in the art for transmitting mixed voice and datasignals without causing abrupt large variations in power consumption.There is also a need in the art for transmitting mixed voice and datasignals without causing sudden large reactions in power control.Further, there is need in the art for transmitting mixed voice and datasignals without causing undue interference within a cell. Moreover,there is a need in the art for transmitting mixed voice and data signalswithout causing undue interference between cells.

SUMMARY

The present invention is directed to a method for power control formixed voice and data transmission. According to various embodiments ofthe invention, mixed voice and data signals are transmitted withoutcausing abrupt large variations in power consumption or sudden largereactions in power control. Further, mixed voice and data signals aretransmitted without causing undue interference within a cell or betweencells.

In one aspect of the invention, a “voice noise power” is added to anaggregate voice power which is the total voice power used by all usersin a cell. The voice noise power is transmitted in addition to theaggregate voice power in order to maintain the total of the aggregatevoice power and voice noise power at a pre-determined voice power limit.Since the aggregate voice power and the voice noise power aresubstantially maintained at a relatively steady level, i.e. at the voicepower limit, power fluctuations within a cell and also in theneighboring cells are significantly diminished. The voice noise powercan be, for example, artificial voice noise which is orthogonally codedor PN coded. In one embodiment, the voice power limit can be increasedor decreased to further improve control over power consumption duringvoice and data transmission.

Further, in order to maintain the power consumed by data transmission ata desired level, data noise is transmitted after transmission of a databurst, or in between data bursts, by inserting a pre-determined amountof artificial data into the gaps in data transmission. The data noise istransmitted in addition to the data bursts in order to maintain thetotal power consumed during data transmission at a desired level. Forexample, the data noise can be transmitted as artificial noise or dummydata, which is orthogonally coded or PN coded. Since the total powerconsumed during data transmission is substantially maintained at adesired level, power fluctuations within a cell and also in theneighboring cells are significantly diminished. In one embodiment, thedesired level for data transmission power consumption can be increasedor decreased to further improve control over power consumption duringvoice and data transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of power control for mixed voice and datatransmission within one cell in a spread spectrum communication system.

FIG. 2A illustrates an example diagram of geographical layout of cellsfor a spread spectrum communication system.

FIG. 2B illustrates an example of power control graphed as a function oftime for cell number 0 of FIG. 2A.

FIG. 2C illustrates an example of power control graphed as a function oftime, over the same time period as FIG. 2B, for cell number 1 of FIG.2A.

FIG. 3 illustrates an example of power control graphed as a function oftime in accordance with one embodiment for a spread spectrumcommunication system.

FIG. 4 also illustrates an example of power control graphed as afunction of time in accordance with another embodiment for a spreadspectrum communication system.

FIG. 5 illustrates an example of power control graphed as a function oftime in accordance with yet another embodiment for a spread spectrumcommunication system.

DETAILED DESCRIPTION

The presently disclosed embodiments are directed to a method for powercontrol for mixed voice and data transmission. The following descriptioncontains specific information pertaining to the implementation of thepresent invention. One skilled in the art will recognize that thepresent invention may be implemented in a manner different from thatspecifically discussed in the present application. Moreover, some of thespecific details of the invention are not discussed in order not toobscure the invention. The specific details not described in the presentapplication are within the knowledge of a person of ordinary skill inthe art.

The drawings in the present application and their accompanying detaileddescription are directed to merely example embodiments of the invention.To maintain brevity, other embodiments of the invention which use theprinciples of the present invention are not specifically described inthe present application and are not specifically illustrated by thepresent drawings.

FIG. 3 illustrates an example of power control in a CDMA communicationsystem in accordance with one embodiment. The general principles of CDMAcommunication systems, and in particular the general principles forgeneration of spread spectrum signals for transmission over acommunication channel is described in U.S. Pat. No. 4,901,307 entitled“Spread Spectrum Multiple Access Communication System Using Satellite orTerrestrial Repeaters” and assigned to the assignee of the presentinvention. The disclosure in that patent, i.e. U.S. Pat. No. 4,901,307,is hereby fully incorporated by reference into the present application.Moreover, U.S. Pat. No. 5,103,459 entitled “System and Method forGenerating Signal Waveforms in a CDMA Cellular Telephone System” andassigned to the assignee of the present invention, discloses principlesrelated to PN spreading, Walsh covering, and techniques to generate CDMAspread spectrum communication signals. The disclosure in that patent,i.e. U.S. Pat. No. 5,103,459, is also hereby fully incorporated byreference into the present application. Further, the present inventionmay utilize time multiplexing of data and various principles related to“high data rate” communication systems, and the present invention can beused in a “high data rate” communication systems, disclosed in U.S.patent application entitled “Method and Apparatus for High Rate PacketData Transmission” Ser. No. 08/963,386 filed on Nov. 3, 1997, andassigned to the assignee of the present invention. The disclosure inthat patent application is also hereby fully incorporated by referenceinto the present application.

Referring back to FIG. 3, graph 300 shows power axis 301 plotted againsttime axis 302. Aggregate voice power Pv 304 for all the voice userswithin the cell is shown in graph 300 as solid curve 304. Aggregatevoice power Pv 304 varies in time as shown in graph 300. Voice powerlimit Pv,max 306 is the maximum voice power allocated for the aggregateof voice signal transmissions. Voice power limit Pv, max 306 is shown ingraph 300 as horizontal double-dotted-dashed line 306. Extra voice poweris allocated in addition to aggregate voice power Pv 304, so that thetotal voice power transmitted at any time is substantially equal tovoice power limit Pv, max 306. The extra voice power, which “fills in”the gap between Pv 304 and Pv, max 306, can be provided, for example, bytransmitting some additional information which is encoded usingorthogonal codes just as if the additional power were being provided foradditional users. In the embodiment shown in FIG. 3, no usefulinformation is transmitted, so the extra voice power is transmitted asartificial noise. It is manifest that useful information can betransmitted using the extra voice power, the details of which areapparent to a person of ordinary skill in the art, and thus are notdescribed here. The artificial noise is shown in FIG. 3 as voice noisepower 308, and also indicated with the word “noise.” Voice noise power308 is encoded using, for example, orthogonal codes as if voice noisepower 308 originated as an ordinary user signal. Thus, other userswithin the cell can still recover their own signal using spread spectrumdespreading techniques such as orthogonal codes despite added voicenoise power 308. In other words, the users within the cell are“protected” from voice noise power 308 by the use of orthogonal codes orPN codes or other means of spreading voice noise power 308.

Continuing with FIG. 3, power is allocated in addition to voice powerlimit Pv,max 306 for transmission of data bursts 310, 312, and 314.Total power Pv+d 316 is the total of aggregate voice power Pv 304 plusthe power allocated for voice noise power 308 plus the power allocatedfor transmission of data bursts 310, 312, and 314. Thus, total powerPv+d 316 may also be stated as the total of Pv, max 306 plus the powerallocated for data burst transmissions. Data power Pdata 324 is thepower used for transmission of data bursts 310, 312, and 314. Thus, bydefinition:

Pv+d=Pdata+Pv,max.

Total power Pv+d 316 is shown in graph 300 as dotted-dashed, steppedline 316. Total power Pv+d 316 varies in time as shown in graph 300. Themaximum available signal transmission power that can be allocated forthe total of aggregate voice, artificial noise, and data transmissionsis maximum total power limit Pmax 318, shown in graph 300 as horizontalsolid line 318 and also indicated by “Pmax”. As seen in graph 300, Pv+d316 remains below maximum power limit Pmax 318.

As discussed above, transmission of data signals typically occurs inbursts, in contrast to transmission of voice signals, where the averagepower level for a number of users is relatively even. Thus, relativelylarge amounts of data are transmitted in bursts at high bit ratesseparated by periods of relative inactivity, or quiet, in which the databit rate is low or data transmission ceases entirely. For example, afterdata burst 310 and before data burst 312, and again after data burst 312and before data burst 314, there is no data available for transmission,i.e. there are gaps in the data transmission. In order to prevent totalpower Pv+d 316 from suddenly dropping, additional data power istransmitted when there are gaps in data transmission to maintain thepower consumed by data transmission, data power Pdata 324, at a desiredlevel. Accordingly, total power Pv+d 316 is maintained at a desiredlevel.

The additional data power, which “fills in” the gap between data burst310 and data burst 312, and the gap between data burst 312 and databurst 314, can be provided, for example, by transmitting some additionalinformation which is encoded using orthogonal codes just as if theadditional power were being provided for additional data users. In theembodiment shown in FIG. 3, no useful data is transmitted, so theadditional data power is transmitted as artificial noise or dummy data.The artificial noise is shown in FIG. 3 as data noise 320, and datanoise 322. Data noise 320 and data noise 322 are encoded, for example,using orthogonal codes as if data noise 320 and data noise 322originated as ordinary data signals. Thus, users within the cell canstill demodulate their own signals without undue interference from datanoise 320 and data noise 322. In other words, the users within the cellare “protected” from data noise 320 and data noise 322 by the use oforthogonal codes or PN codes or other means of spreading data noise 320and data noise 322.

FIG. 3 shows an example interaction of mixed voice and data signaltransmission with power control in accordance with one embodiment. Theamount of data power, Pdata 324, allocated to data burst 310 iscontrolled as a percentage of voice power limit Pv, max 306 rather thanallocating the full amount of power which might be required to transmitdata burst 310 as quickly as possible. For initial data burst 310, Pdata324 is limited, for example, to 10% of Pv, max 306. Then, for example,for subsequent data burst 312, Pdata 324 is increased or adjusted upwardby pre-determined amounts of 5% of Pv, max 306 as required to transmitthe data at a reasonable rate. For example, Pdata 324 can be increasedsubject to specific conditions relating to the amount of data noise andactual data that have recently been transmitted. For example, thecondition can be that the actual data transmitted, i.e. the amount ofdata transmitted in data burst 310, is 95% or more of the total powertransmitted and that the data noise transmitted is 5% or less of thetotal power transmitted. Conversely, Pdata 324 can be decreased oradjusted downward by pre-determined amounts, for example, when theactual data transmitted is 50% or less of the total power transmittedand the data noise transmitted is 50% or more of the total powertransmitted. In general, the pre-determined and pre-defined amounts forthe adjustments can be any amounts between 0% and approximately 15%; 5%and 10% are used only as examples for illustrative purposes. Forsubsequent data burst 314, no further adjustments of Pdata 324 arerequired. As seen in the equation Pv+d=Pdata+Pv, max, total power Pv+d316 is limited by the pre-determined increases in Pdata 324.

As shown in FIG. 3, filling Pv, max 306 with voice noise 308; increasingtotal power Pv+d 316 by pre-determined amounts; and filling in Pv+d 316by inserting data noise such as data noise 320 between consecutive databursts 310 and 312 have the effect of eliminating large swings,overshoots, and instability in the allocation of aggregate voice powerPv 304. For example, filling in Pv+d 316 by inserting data noise such asdata noise 320 between consecutive data bursts 310 and 312 prevents theoverreactions of the power control system to large sudden changes indata power level, discussed in connection with FIG. 1, by eliminatingsuch large sudden changes when there are gaps in the data transmission.As a result, aggregate voice power Pv 304 changes smoothly. Increasingtotal power Pv+d 316 by pre-determined amounts also results ineliminating large sudden changes when there are transitions from “quietperiods” to transmitting data bursts or when there are large increasesin the rate or amount of data being transmitted by the communicationsystem. Moreover, filling Pv, max 306 with voice noise 308 prevents thefeedback effect between cells discussed in connection with FIG. 2 bykeeping the voice power, “seen” by other cells as noise, at a constantlevel, i.e. Pv, max 306. Keeping the voice power at a constant levelfurther prevents large swings in the voice power, such as those seen inFIG. 2C, and thus prevents reactions of neighboring cells to thoseswings. As a result, the intra-cell power control problems discussedabove in connection with FIG. 1 are avoided, and the inter-cell powercontrol problems discussed above in connection with FIG. 2 are alsoavoided.

FIG. 4 illustrates another example of power control in a CDMAcommunication system in accordance with one embodiment. FIG. 4 showsgraph 400, having power axis 401 plotted against time axis 402.Aggregate voice power Pv 404 for all voice users within the cell isshown in graph 400 as solid curve 404. Aggregate voice power Pv 404varies in time as shown in graph 400. Voice power limit Pv,max 406 isthe maximum voice power allocated for the aggregate of voice signaltransmissions. Voice power limit Pv, max 406 is shown in graph 400 asdouble-dotted-dashed, stepped line 406. Extra voice power is allocatedin addition to aggregate voice power Pv 404, so that the total voicepower transmitted at any time is substantially equal to voice powerlimit Pv, max 406. The extra voice power is voice noise power 408, which“fills in” the gap between Pv 404 and Pv, max 406. As discussed above,voice noise power 408 is typically provided by transmitting artificialnoise which is coded or spread the same way as other user signals sothat the users within a cell can recover their own signal using spreadspectrum despreading techniques despite added voice noise power 408.

When no useful information is transmitted using voice noise power 408,it is to the advantage of the system to minimize the amount of powerconsumed by voice noise power 408. FIG. 4 shows an example of adaptingvoice power limit Pv, max 406 in accordance with one embodiment.Adapting voice power limit Pv, max 406 has the effect of reducing theamount of power consumed by transmission of voice noise power 408, forexample, in comparison with voice noise power 308 in the example shownin FIG. 3. Adaptation of voice power limit Pv, max 406 can be achievedin many ways. For example, voice power limit Pv, max 406 can be adjustedto pre-set levels in response to a change in usage in order to reflectperiods of greater or lesser usage. Usage can be measured according tovarious criteria. For example, usage can be measured as the percentageutilization of the total system capacity based on the number of usersactually using the system at a particular time compared to the maximumnumber of users the system can accommodate. As another example, usagecan be measured as the percentage utilization of available transmitpower by comparing the value of aggregate voice power Pv 404 to thevalue of maximum power limit Pmax 418, described below. The response tochange in usage can be dynamic, or the response can be scheduled forcertain times of day. Voice power limit Pv, max 406 can be set to ahigher limit at the beginning of a “busy hour”, for example, and thenreset to a lower limit at the end of the busy hour.

Continuing with FIG. 4, power is allocated in addition to voice powerlimit Pv,max 406 for transmission of data bursts 410, 412, and 414.Total power Pv+d 416 is the total of aggregate voice power Pv 404 plusthe power allocated for voice noise power 408 plus the power allocatedfor transmission of data bursts 410, 412, and 414. Thus, total powerPv+d 416 may also be stated as the total of Pv, max 406 plus the powerallocated for data burst transmissions. Data power Pdata 424 is thepower used for transmission of data bursts 410, 412, and 414. Thus, bydefinition:

Pv+d=Pdata+Pv,max.

Total power Pv+d 416 is shown in graph 400 as dotted-dashed, steppedline 416. Total power Pv+d 416 varies in time as shown in graph 400. Themaximum available signal transmission power that can be allocated forthe total of aggregate voice, artificial noise, and data transmissionsis maximum total power limit Pmax 418, shown in graph 400 as horizontalsolid line 418 and also indicated by “Pmax”. As seen in graph 400, Pv+d416 remains below maximum power limit Pmax 418.

As discussed above, transmission of data typically occurs in bursts. Inorder to prevent total power Pv+d 416 from suddenly dropping, additionaldata power is transmitted when there are gaps in the data transmissionto maintain the power consumed by data transmission, data power Pdata424, at a desired level. Accordingly, total power Pv+d 416 is maintainedat a desired level. The additional data power, which “fills in” the gapbetween data burst 410 and data burst 412, and the gap between databurst 412 and data burst 414, is data noise 420 and data noise 422. Asdiscussed above, data noise 420 and data noise 422 can be provided bytransmitting artificial noise or dummy data, which is coded or spreadthe same way as other user data signals. Thus, the users within the cellcan recover their own signal using spread spectrum despreadingtechniques despite added data noise 420 and data noise 422.

FIG. 4 also shows an example interaction of mixed voice and data signaltransmission with power control in accordance with one embodiment. Theamount of data power, Pdata 424, allocated to data burst 410 iscontrolled as a percentage of voice power limit Pv, max 406 rather thanallocating the full amount of power which might be required to transmitdata burst 410 as quickly as possible. For initial data burst 410, Pdata424 is limited, for example, to 10% of Pv, max 406. Then, for example,for subsequent data burst 412, Pdata 424 is increased by pre-determinedamounts of 5% of Pv,max 406 as required to transmit the data at areasonable rate. For example, Pdata 424 can be increased subject tospecific conditions relating the amount of data noise and actual datathat have recently been transmitted. For example, the condition can bethat the actual data transmitted, i.e. the amount of data transmitted indata burst 410, is 95% or more of the total power transmitted and thatthe data noise transmitted is 5% or less of the total power transmitted.In general, the pre-determined and pre-defined amounts for theadjustments can be any amounts between 0% and approximately 15%; 5% and10% are used only as examples for illustrative purposes. For subsequentdata burst 414, no further adjustments of Pdata 424 are required. Asseen in the equation Pv+d=Pdata+Pv, max, total power Pv+d 416 is limitedby the pre-determined increases in both Pdata 424 and Pv, max 406.

As shown in FIG. 4, adapting voice power limit Pv, max 406; filling Pv,max 406 with voice noise 408; increasing total power Pv+d 416 bypre-determined amounts; and filling in Pv+d 416 by inserting data noisesuch as data noise 420 between consecutive data bursts 410 and 412 havethe effect of eliminating large swings, overshoots, and instability inthe allocation of aggregate voice power Pv 404. For example, filling inPv+d 416 by inserting data noise such as data noise 420 betweenconsecutive data bursts 410 and 412 prevents the overreactions of thepower control system to large sudden changes in data power level,discussed in connection with FIG. 1, by eliminating such large suddenchanges when there are gaps in the data transmission. As a result,aggregate voice power Pv 404 changes smoothly. Increasing total powerPv+d 416 by pre-determined amounts also results in eliminating largesudden changes when there are transitions from “quiet periods” totransmitting data bursts or when there are large increases in the rateor amount of data being transmitted by the communication system.Moreover, filling Pv, max 406 with voice noise 408 prevents the feedbackeffect between cells discussed in connection with FIG. 2 by limiting thevoice power, “seen” by other cells as noise, to slow, smooth, gradualchanges, i.e. Pv, max 406 is constrained to pre-defined adjustments.Limiting the voice power to gradual changes further prevents largeswings in the voice power, such as those seen in FIG. 2C, and thusprevents reactions of neighboring cells to those swings.

As a result, the intra-cell power control problems discussed above inconnection with FIG. 1 are avoided, and the inter-cell power controlproblems discussed above in connection with FIG. 2 are also avoided.Furthermore, adaptation of voice power limit Pv, max 406 improves theefficiency and the economy of power control in the communication systemby minimizing the amount of extra power used for voice noise filling.

FIG. 5 illustrates a further example of power control in a CDMAcommunication system in accordance with one embodiment. FIG. 5 showsgraph 500, having power axis 501 plotted against time axis 502.Aggregate voice power Pv 504 for all voice users within the cell isshown in graph 500 as solid curve 504. Aggregate voice power Pv 504varies in time as shown in graph 500. Voice power limit Pv,max 506 isthe maximum voice power allocated for the aggregate of voice signaltransmissions. Voice power limit Pv, max 506 is shown in graph 500 asdouble-dotted-dashed, stepped line 506. Extra voice power is allocatedin addition to aggregate voice power Pv 504, so that the total voicepower transmitted at any time is substantially equal to voice powerlimit Pv, max 506. The extra voice power is voice noise power 508, which“fills in” the gap between Pv 504 and Pv, max 506. As discussed above,voice noise power 508 is typically provided by transmitting artificialnoise, which is coded or spread the same way as other user signals.Thus, the users within a cell can recover their own signal using spreadspectrum despreading techniques despite added voice noise power 508.

When no useful information is transmitted using voice noise power 508,it is to the advantage of the system to minimize the amount of powerconsumed by voice noise power 508. FIG. 5 shows an example of adaptingvoice power limit Pv, max 506 in accordance with one embodiment.Adapting voice power limit Pv, max 506 has the effect of reducing theamount of power consumed by transmission of voice noise power 508 incomparison with the case in which a voice power limit, such as voicepower limit Pv, max 306 shown in FIG. 3, is not adapted. Adaptation ofvoice power limit Pv, max 506 can be achieved in many ways. For example,voice power limit Pv, max 506 can be adjusted to pre-set levels inresponse to a change in usage or at certain times of the day in order toreflect periods of greater or lesser usage. Voice power limit Pv, max506 can be set to a higher limit at the beginning of a “busy hour”, forexample, and then reset to a lower limit at the end of the busy hour.

Continuing with FIG. 5, power is allocated in addition to voice powerlimit Pv,max 506 for transmission of data bursts 510, 512, and 514.Total power Pv+d 516 is the total of aggregate voice power Pv 504 plusthe power allocated for voice noise power 508 plus the power allocatedfor transmission of data bursts 510, 512, and 514. Thus, total powerPv+d 516 may also be stated as the total of Pv, max 506 plus the powerallocated for data burst transmissions. Data power Pdata 524 is thepower used for transmission of data bursts 510, 512, and 514. Thus, bydefinition:

Pv+d=Pdata+Pv,max.

Total power Pv+d 516 is shown in graph 500 as dotted-dashed, steppedline 516. Total power Pv+d 516 varies in time as shown in graph 500. Themaximum available signal transmission power that can be allocated forthe total of aggregate voice, artificial noise, and data transmissionsis maximum total power limit Pmax 518, shown in graph 500 as horizontalsolid line 518 and also indicated by “Pmax”. As seen in graph 500, Pv+d516 remains below maximum power limit Pmax 518.

As discussed above, transmission of data typically occurs in bursts. Inorder to prevent total power Pv+d 516 from suddenly dropping, additionaldata power is transmitted when there are gaps in the data transmissionto maintain the power consumed by data transmission, data power Pdata524, at a desired level. Accordingly, total power Pv+d 516 is maintainedat a desired level. The additional data power, which “fills in” the gapbetween data burst 510 and data burst 512, is data noise 520. Similarly,data noise 522 is transmitted to maintain the level of total power Pv+d516 after the end of data burst 512, although there is no data bursttransmitted subsequent to the transmission of data noise 522. It iswasteful, however, to continue transmission of data noise 522 for verylong if there is no subsequent data to transmit or if the datatransmission rate has fallen low enough that substantially less powershould be allocated to data transmission. In other words, data powerPdata 524 should be reduced or adjusted to a lower level.

Therefore, data noise 522 is transmitted subject to specific conditionsrelating the amount of data noise and actual data that have recentlybeen transmitted. For example, the condition can be that the data noisetransmitted is equal to or greater than the actual data transmitted.Then, if the amount of data noise 522 is equal to or greater than theamount of data transmitted in data burst 512, then data power Pdata 524will be reduced or decreased by a pre-determined amount to a lowerlevel. For example, the pre-determined amount can be equal to 10% ofvoice power limit Pv, max 506. FIG. 5 shows data noise 523 transmittedat a level of data power Pdata 524, which is reduce by 10% of voicepower limit Pv, max 506 from the level of data noise 522. In general,the pre-determined and pre-defined amounts for the adjustments can beany amounts between 0% and approximately 15%, and 5% and 10% are used asexamples only for illustrative purposes.

As no further data is transmitted, data power Pdata 524 continues to bereduced, for example, by a pre-determined amount equal to 10% of voicepower limit Pv, max 506 for each reduction, during the transmission ofdata noise 523. Thus, the example in FIG. 5 shows a “stepped” appearancefor data noise 523. In addition, the example of FIG. 5 shows voice powerlimit Pv, max 506 being reduced by amounts equal to approximately 10% ofvoice power limit Pv, max 506 during the transmission of data noise 523.Thus, total power Pv+d 516, which is the sum of data power Pdata 524 andvoice power limit Pv, max 506, is shown in graph 500 as decreasingduring the transmission of data noise 523 in response to both thereductions in voice power and in data power. As seen in the equationPv+d=Pdata+Pv, max, total power Pv+d 516 is limited by thepre-determined decreases in both Pdata 524 and Pv, max 506.

Data noise 520, data noise 522, and data noise 523 can be provided bytransmitting artificial noise or dummy data, which is coded or spreadthe same way as other user data signals, as discussed above. Thus, theusers within the cell can recover their own signals using spreadspectrum despreading techniques despite added data noise 520, data noise522, and data noise 523.

As shown in FIG. 5, adapting voice power limit Pv, max 506; filling Pv,max 506 with voice noise 508; reducing data power Pdata 524 inpre-determined amounts; and filling in Pv+d 516 by inserting data noisesuch as data noise 520 between consecutive data bursts 510 and 512 or byinserting data noise such as data noise 523 when reducing data powerPdata 524 have the effect of eliminating large swings, overshoots, andinstability in the allocation of aggregate voice power Pv 504. Forexample, filling in Pv+d 516 by inserting data noise such as data noise520 between consecutive data bursts 510 and 512 prevents theoverreactions of the power control system to large sudden changes indata power level, discussed in connection with FIG. 1, by eliminatingsuch large sudden changes when there are gaps in the data transmission.As a result, aggregate voice power Pv 504 changes smoothly. Reducingtotal power Pv+d 516 by pre-determined amounts also results ineliminating large sudden changes when there are transitions fromtransmitting data bursts to “quiet periods” or when there are largedecreases in the rate or amount of data being transmitted by thecommunication system. Moreover, filling Pv, max 506 with voice noise 508prevents the feedback effect between cells discussed in connection withFIG. 2 by limiting the voice power, “seen” by other cells as noise, toslow, smooth, gradual changes, i.e. Pv, max 506 is constrained topre-defined adjustments. Limiting the voice power to gradual changesfurther prevents large swings in the voice power, such as those seen inFIG. 2C, and thus prevents reactions of neighboring cells to thoseswings.

As a result, the intra-cell power control problems discussed above inconnection with FIG. 1 are avoided, and the inter-cell power controlproblems discussed above in connection with FIG. 2 are also avoided.Furthermore, adaptation of voice power limit Pv, max 506 improves theefficiency and the economy of power control in the communication systemby minimizing the amount of extra power used for voice noise filling. Inaddition, limiting and reducing data power Pdata 524, improves theefficiency and the economy of power control in the communication systemby minimizing the amount of extra power used for data noise filling.

It is appreciated by the above detailed disclosure that the inventionprovides a method and system of power control for mixed voice and datatransmissions in a CDMA communication system. Although the invention isdescribed as applied to communications in a CDMA system, it will bereadily apparent to a person of ordinary skill in the art how to applythe invention in similar situations where power control for mixed voiceand data signal transmission is needed.

From the above description, it is manifest that various techniques canbe used for implementing the concepts of the present invention withoutdeparting from its scope. Moreover, while the invention has beendescribed with specific reference to certain embodiments, a person ofordinary skill in the art would recognize that changes can be made inform and detail without departing from the spirit and the scope of theinvention. For example, the voice noise filling presented in oneembodiment described here can be omitted so that data power is allocateddirectly on top of voice power without departing from the method of datanoise filling and smoothly allocating data power presented in oneembodiment described here. Also, for example, different techniques canbe employed for measuring interference, transmitting artificial voicenoise and artificial data noise, and adjusting the power allocated tothe transmitted signal. Further, the type of information used for voicenoise and data noise filling and the type of coding or spreading usedmay differ from that presented in one embodiment described here. Thedescribed embodiments are to be considered in all respects asillustrative and not restrictive. It should also be understood that theinvention is not limited to the particular embodiments described herein,but is capable of many rearrangements, modifications, and substitutionswithout departing from the scope of the invention.

Thus, a method for power control for mixed voice and data transmissionhas been described.

1. A method for power control of mixed voice and data transmissions,comprising: transmitting a voice signal at a dynamically-adjusted voicetransmit power capped at a maximum voice transmit power limit;concurrently transmitting data bursts on top of the voice signal; andinserting data noise between the data bursts transmissions, where thedata burst and inserted data noise are transmitted at adynamically-adjusted data transmit power based on the voice transmitpower to restrict the rate of change of the data transmit power until amaximum data transmit power limit is reached.
 2. The method of claim 1,wherein the dynamically-adjusted data transmit power is adjusted as apercentage of the dynamically-adjusted voice transmit power.
 3. Themethod of claim 1, further comprising: adding a voice noise at a voicenoise power on top of the voice signal, the aggregate of the voice noisepower and vice transmit power is substantially equal to the maximumvoice transmit power limit.
 4. The method of claim 1, wherein themaximum voice transmit power limit is dynamically-adjusted from a lowerlimit to an upper limit.
 5. The method of claim 1, wherein the maximumvoice transmit power limit is predetermined.
 6. The method of claim 1,wherein the maximum voice transmit power limit is dynamically adjusted.7. The method of claim 1, wherein dynamically-adjusted data transmitpower increases from a minimum data transmit power limit to the maximumdata transmit power limit.
 8. The method of claim 1, wherein thedynamically-adjusted data transmit power decreases from the maximum datatransmit power limit to a minimum data transmit power limit.
 9. Themethod of claim 1, wherein the dynamically-adjusted data transmit poweris adjusted by approximately 5% of the maximum voice transmit powerlimit at any one time.
 10. The method of claim 1, wherein thedynamically-adjusted data transmit power is adjusted by between 0 and15% of the maximum voice transmit power limit at any one time.
 11. Themethod of claim 1, wherein the dynamically-adjusted data transmit poweris adjusted by between 5 and 10% of the maximum voice transmit powerlimit at any one time.
 12. An apparatus adapted for power control ofmixed voice and data transmissions, comprising: means for transmitting avoice signal at a dynamically-adjusted voice transmit power capped at amaximum voice transmit power limit; means for concurrently transmittingdata bursts on top of the voice signal; and means for inserting datanoise between the data bursts transmissions, where the data burst andinserted data noise are transmitted at a dynamically-adjusted datatransmit power based on the voice transmit power to restrict the rate ofchange of the data transmit power until a maximum data transmit powerlimit is reached.
 13. The apparatus of claim 12, wherein thedynamically-adjusted data transmit power is adjusted as a percentage ofthe dynamically-adjusted voice transmit power.
 14. The apparatus ofclaim 12, wherein the maximum voice transmit power limit isdynamically-adjusted from a lower limit to an upper limit.
 15. Theapparatus of claim 12, further comprising: means for adding a voicenoise at a voice noise power on top of the voice signal, the aggregateof the voice noise power and vice transmit power is substantially equalto the maximum voice transmit power limit.
 16. The apparatus of claim12, wherein the maximum voice transmit power limit is predetermined. 17.The apparatus of claim 12, wherein the maximum voice transmit powerlimit is dynamically adjusted.
 18. The apparatus of claim 12, whereindynamically-adjusted data transmit power increases from a minimum datatransmit power limit to the maximum data transmit power limit.
 19. Theapparatus of claim 12, wherein the dynamically-adjusted data transmitpower decreases from the maximum data transmit power limit to a minimumdata transmit power limit.
 20. The apparatus of claim 12, wherein thedynamically-adjusted data transmit power is adjusted by approximately 5%of the maximum voice transmit power limit at any one time.
 21. Theapparatus of claim 12, wherein the dynamically-adjusted data transmitpower is adjusted by between 0 and 15% of the maximum voice transmitpower limit at any one time.
 22. The apparatus of claim 12, wherein thedynamically-adjusted data transmit power is adjusted by between 5 and10% of the maximum voice transmit power limit at any one time.
 23. Amethod for power control of mixed voice and data transmissions,comprising: transmitting a mixed signal at a total transmit power, themixed signal including voice, data bursts, and inserted data noise, andthe total transmit power is the aggregation of a voice transmit powerand a data transmit power; and dynamically-adjusting the total transmitpower by limiting its rate of change over time by the insertion of thedata noise.